That was a slowdown of 0.5 percentage points from June. Worse, it came despite some easy comparisons from a year ago, when same-store sales fell 3%.

The numbers suggest that consumers are shifting their restaurant behavior in midsummer, or perhaps they are indicative of an overall industry slowdown that has been ongoing for three years now. There were no factors such as weather or other issues that could have pulled down sales during the month.

“We’re not able to solve the real underlying issues, where we keep losing traffic to competitors,” said Victor Fernandez, vice president of insights and knowledge at Black Box parent company TDn2K.

The biggest problem is a persistent decline in guest counts. Same-store traffic fell 1.8%. But on a two-year, stacked basis, it’s far worse than that: down 6.6%.

Customers are paying more. But there are fewer of them.

“What we’ve been able to do in recent months is get people to spend more,” Fernandez said. “That’s what’s kept us above water.”

The poor sales and traffic come despite an improving economy. Unemployment is below 4% and the economy is in an expansion mode.

And tax cuts approved early this year were supposed to have an impact on industry sales at some point. That has not happened.

Yet wage gains remain relatively limited. And trade skirmishes between the U.S. and other nations also threaten to keep the economy at bay.

That could keep restaurant spending in check for a while.

“While expectations are for restaurant spending to continue to expand slowly,” said Joel Naroff, president of Naroff Economic Advisors and TDn2K's economist, in a statement, “the risks appear to be on the side of a moderation in demand as we go into 2019.”

Yet it’s uncertain why July in particular has been such a problem. Fernandez called the month “an anomaly.”

He suggested that the numbers reflect an ongoing change in the way consumers are using restaurants.

Independents in many markets have gained an upper hand in recent years as consumers use ratings sites such as Yelp and other sources to find new restaurants. That could be hurting chains as consumers on vacations shift more spending to independents and smaller concepts that aren’t captured in the index.

“As you travel and take the family car and drive to the beach, in the past you’d go to a chain restaurant because it was familiar and you knew where it was,” Fernandez said. “More and more, people want to get away from that and find something they haven’t found before.”

Some key tests will come in the next three months. A year ago, same-store sales were hurt in August and especially September as hurricanes hit Texas and Florida. And then those same-store sales rebounded in October.

If sales don’t improve much in the next two months, absent some external factor, then the industry will have a bigger challenge on its hands. And even if sales appear to be strong, that could be a false positive.

“That may be an artificial sense of strength for the industry based on that,” Fernandez said. “If from the next two months we don’t see strong numbers, there could be concern there.”